1. Field
The present disclosure relates generally to motion sensing in mobile communication devices and, more particularly, to radio frequency (RF) ranging-assisted local motion sensing for use in and/or with mobile communication devices.
2. Information
Mobile or wireless communication devices, such as, for example, cellular telephones, personal digital assistants, electronic book readers, and/or the like have become more common place in daily life. As geographic barriers to personal travel decrease and society becomes more mobile, the need to access information regardless of place and/or time, as well as to stay connected while on the move becomes increasingly important. The use of the Internet, e-mail, electronically-enabled trade or e-commerce, etc., has become widespread, and mobile communication devices may already play a significant role in allowing society to maintain its mobility. Continued advancements in information technology, communications, mobile applications, etc. help to contribute to a rapidly growing market for mobile communication devices, which have become ubiquitous and may already be viewed as “extensions of the hand” altering the manner in which society communicates, does business, and/or creates value.
Mobile communication devices may include a variety of sensors to support a number of applications. Typically, although not necessarily, such sensors may convert physical phenomena into analog and/or digital electrical signals and may be integrated into (e.g., built-in, etc.) or otherwise supported by (e.g., stand-alone, external, etc.) a mobile communication device. For example, these sensors may include inertial or motion sensors (e.g., accelerometers, gyroscopes, compasses, magnetometers, gravitometers, etc.), ambient environment sensors (e.g., ambient light detectors, proximity sensors, vibrational sensors, thermometers, cameras, etc.), or other sensors capable of measuring various states of a mobile communication device. The above sensors, as well as other possible sensors, may be utilized individually or may be used in combination with other sensors, depending on a particular application.
A popular and rapidly growing market trend in sensor-based mobile communications technology includes applications that may recognize one or more aspects of a motion of a mobile communication device and use such aspects as a form of input (e.g., task-oriented or informative hand gestures, wrist-based tilt gestures, etc.), for example, in motion-based or motion-controlled games, web page navigation, image browsing, etc. Typically, although not necessarily, these popular motion-based applications utilize one or more built-in inertial or motion sensors (e.g., accelerometers, magnetometers, etc.), that may, for example, sense and/or measure the direction of gravity, spatial orientation, linear and/or angular motion, and/or other force or field experienced by a mobile communication device. These sensors, however, utilize the Earth's gravitational and/or magnetic fields as an external or global reference frame and, as such, detect and/or measure a motion of a mobile communication device that is global, such as, for example, a motion of the device relative to the Earth-centered coordinates. On the contrary, mobile-based applications typically, although not necessarily, are adapted to act upon a motion that is user-centric or local with respect to a particular user (e.g., local reference frame, etc.), for example, in an attempt to avoid or reduce false positives and/or negatives in detecting user inputs. Such a local motion may include, for example, a movement of the user's hand (e.g., holding a mobile communication device) relative to the user's body or a part of the user's body (e.g., shoulders, head, knees, etc.) representing one or more local references.
Typically, although not necessarily, motion sensors may be able to differentiate between a global and a local motion of a mobile communication device, for example, while a user remains stationary or substantially stationary with respect to the ground (e.g., an external reference frame), such as while a user is standing, sitting, etc. without a change in the user location, position, orientation, etc. However, if a user is operating a mobile communication device, for example, while walking, running, driving an accelerating and/or decelerating vehicle, or being on board of an unsteady (e.g., moving, rocking, etc.) ship, train, etc., motion sensors may not be able to sufficiently differentiate between a global motion and a local motion of the device. For example, in certain situations, a global motion may comprise a combined motion incorporating multiple levels and/or types of motions, such as a motion of a user operating a mobile communication device (e.g., via an input gesture, etc.), a motion of a user's concurrent (e.g., with operating a mobile device) walking or running, a motion of an accelerating and/or decelerating vehicle with a user on-board, etc. Accordingly, continued integration of various acceleration and/or deceleration vectors associated with such multiple motions may lead to drifts (e.g., bias in detections of a mobile device being in motion and being relatively still), thus, potentially “confusing” or otherwise negatively impacting an operation of a motion-based application hosted on the mobile device. Built-in digital cameras may partially help to compensate for such vector displacements and/or lack of a stable local reference frame, but may remain unaware of important aspects of user-device interactions in many different and changing mobile environments due to, for example, light levels, proximity of other people or objects, unwanted target acquisitions, and/or the like. Also, utilizing background sensing, frame stabilizing (e.g., by analyzing optical flow, periphery of the image acquisition area, etc.), and/or like techniques, for example, to detect and/or measure foreground (e.g., local) motion or activity may not provide a sufficiently complete or feasible solution in mobile settings or environments. Accordingly, it may be desirable to develop one or more methods, systems, and/or apparatuses that may implement effective and/or efficient local motion sensing regardless of whether a user remains stationary, walking, being on board of accelerating and/or decelerating vehicles, etc. for more satisfying user experience.